Researchers test an experimental drug or treatment in a small group of people (20-80), to evaluate its safety and identify side effects. Often these trials are not disease specific and may include more than one type of cancer.

The experimental drug or treatment is administered to a larger group of people (100-300) to determine its effectiveness and to further evaluate its safety.

The experimental drug or treatment is administered to larger groups of people (1,000-3,000) to confirm its effectiveness, monitor side effects, compare it with standard or equivalent treatment, and collect information that will allow the experimental drug or treatment to be used safely.